From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1LYWK6-0001yA-H8 for qemu-devel@nongnu.org; Sat, 14 Feb 2009 21:01:34 -0500 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1LYWK4-0001xw-U9 for qemu-devel@nongnu.org; Sat, 14 Feb 2009 21:01:34 -0500 Received: from [199.232.76.173] (port=46407 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1LYWK4-0001xt-Om for qemu-devel@nongnu.org; Sat, 14 Feb 2009 21:01:32 -0500 Received: from mail2.shareable.org ([80.68.89.115]:38438) by monty-python.gnu.org with esmtps (TLS-1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.60) (envelope-from ) id 1LYWK4-0005KD-6y for qemu-devel@nongnu.org; Sat, 14 Feb 2009 21:01:32 -0500 Received: from jamie by mail2.shareable.org with local (Exim 4.63) (envelope-from ) id 1LYWJy-0002YK-Dv for qemu-devel@nongnu.org; Sun, 15 Feb 2009 02:01:26 +0000 Date: Sun, 15 Feb 2009 02:01:26 +0000 From: Jamie Lokier Subject: Re: [Qemu-devel] [PATCH] Revert block-qcow2.c to kvm-72 version due to corruption reports Message-ID: <20090215020126.GA9281@shareable.org> References: <4988AD96.6090308@codemonkey.ws> <20090213084023.GA1020@kos.to> <20090213163043.GJ18471@shareable.org> <4995A723.9010208@codemonkey.ws> <20090213190419.GB20328@shareable.org> <4997502D.1080401@codemonkey.ws> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4997502D.1080401@codemonkey.ws> Reply-To: qemu-devel@nongnu.org List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Anthony Liguori wrote: > Well such a large reversion is a bad idea. Can you git bisect to the > actual changeset that introduced the bug you see? Have done, did you read the other thread? Message-ID: <20090211114126.GC31997@shareable.org> Subject: Re: qcow2 corruption observed, fixed by reverting old change Jamie Lokier wrote: > Kevin Wolf wrote: > > Jamie Lokier schrieb: > > > Although there are many ways to make Windows blue screen in KVM, in > > > this case I've narrowed it down to the difference in > > > qemu/block-qcow2.c between kvm-72 and kvm-73 (not -83). > > > > This must be one of SVN revisions 5003 to 5008 in upstream qemu. Can you > > narrow it down to one of these? I certainly don't feel like reviewing > > all of them once again. > > It's QEMU SVN delta 5005-5006, copied below. I don't have time to disentangle the different optimisations done to qcow2 around that changeset, nor fix the changeset itself, but I can test proposed patches on my guest VM image, which I've copied aside because it's consistent about failing or not. If nobody else has time either, then I think an imminent new QEMU release, which may get rolled into distros and so on, is better off with the the changes reverted than corrupting guest images. I'm not proposing throwing away all the good work done on qcow2, only that fixing observed corruption is important especially for a major release, and reverting later changes can be temporary until the bug is found and fixed. -- Jamie